Organic peroxyacids have long been known for their excellent bleaching activity. For instance, U.S. Pat. No. 4,642,198 (Humphreys et al) describes a variety of water-insoluble organic peroxyacids intended for suspension in an aqueous, low pH liquid. The preferred peroxy material is 1,12-diperoxydodecanedioic acid (DPDA). Surfactants, both anionic and nonionic, are utilized as suspending agents. When formulated with 10% surfactant, DPDA exhibits good stability under storage conditions. When the surfactant level of the formulation is increased to 22%, a level typical for a heavy-duty laundry detergent, the half-life of the DPDA decreases dramatically. For example, U.S. Pat. No. 4,992,194 (Liberti et al) reports that at 40.degree. C. the half-life of DPDA is only 1 to 2 weeks in a pH 4-4.5 heavy-duty laundry liquid.
EP 0 349 940 (Hoechst AG) describes a series of imido peroxyacids, chief among which is N-phthaloylamino peroxycaproic acid (PAP). Suspension of imidoperoxycarboxylic acids in an aqueous system is achieved through use of sodium alkylbenzene sulfonate as reported in EP 0 435 379 (Akzo N. V.). Related technology in EP 0 347 724 (Ausimont) discloses heterocyclic peracids such as N-acyl-piperidine percarboxylic acids. WO 90/14336 (Interox) discloses 6,6'-terephthal-di(amidoperoxyhexanoic) acid and 6,6'-fumaryl bis (amidoperoxyhexanoic) acid.
Oxygen-releasing materials have an important limitation, however, their activity is extremely temperature dependent. Temperatures in excess of 60.degree. C. are normally required to achieve any bleach effectiveness in an aqueous wash system. The art has partially solved this problem through the use of activators. These activators, also known as bleach precursors or oxidation catalyst, react with oxygen releasing materials to generate more effective oxidizing species.
A variety of sulfonimine complexes used as oxidation catalysts have been described in U.S. Pat No. 5,047,163 (Batal et al.).
It has been surprisingly found that the bleaching activity of the organic peroxyacids having a percarboxylic and a carboxylic acid, or a salt functional unit, in combination with a sulfonimine catalyst is significantly improved under alkaline conditions.
It is thus an object of the present invention to provide novel peroxycarboxylic acids in combination with sulfonimine catalysts to provide an improved bleaching system and detergent composition containing such system.
It is another object of the present invention to improve the performance of the new peroxycarboxylic acids and sulfonimine catalysts bleaching system in highly alkaline detergent formulations.
A further object of the present invention is to provide a bleaching system which operates over a wide temperature range including those temperatures under 60.degree. C.
Another object of the present invention is to provide bleach improvement through the combination of novel peroxycarboxylic acids and sulfonimine catalysts which are effective in relatively small amounts to provide stable compositions and to avoid substantial incremental cost.
A still further object of the present invention is to provide a method for bleaching stained surfaces such as clothes, household hard surfaces including sinks, toilets and the like, dishware and even dentures.
These and other objects will become apparent through the following description of the invention.